1. Field of the Invention
The present invention relates to an image display apparatus.
2. Description of the Background Art
A conventional image display apparatus is disclosed in Japanese Patent Application Laid-Open No. 10-322622 (1998), for example (which is hereinafter referred to as Patent Document 1). In the digital television receiver described in Patent Document 1, output video characteristics and output audio characteristics are set according to the genre and the tastes of a user, on the basis of genre information transmitted together with the digital broadcast content from the broadcast station.
Also, a method for characterizing video content is disclosed in Japanese Patent Application Laid-Open No. 2002-520747 (which is hereinafter referred to as Patent Document 2), for example. The histogram method of Patent Document 2 for characterizing video content identifies key frames from the video content, generates histograms from the key frames, and categorizes the histograms to find program boundaries and to search for video content.
Also, an image processing apparatus described in Japanese Patent Application Laid-Open No. 2004-7301 (which is hereinafter referred to as Patent Document 3) achieves improved image quality by obtaining a relation between luminance signal of the input video signal and frequencies of appearance, from a cumulative histogram about the luminance signal, selecting a gray-level pattern suitable for the video, and correcting the video signal on the basis of the selected gray-level pattern.
In patent Document 1, the genre information is transmitted together with the content information in digital broadcasting such as CS broadcasting. That is, the content information is not contained in conventional analog broadcasting and recorded videos such as DVDs and the like. Also, the transmitted video genre information is not always classified in the same categories of genres as those classified by the viewer. For example, whether the content is an animation or a movie is determined according to the information transmitted from the broadcast station, and the genre may differ from the categorization by the viewer.
In Patent Document 2, it is impossible to judge the genre of video in a real-time manner, because the genre is judged by identifying key frames, generating histograms, and grouping the histograms, so as to search for program boundaries and programs.
Thus, the amount of characterization of video is extracted from luminance histograms about the input video signal, and image processing is performed in correspondence with the characterization of the content, but the image processing might work undesirably because the amount of characterization obtained from one frame of image signal is not stable even in the same genre.
In Patent Document 3, the gray levels of video signal are corrected on the basis of a gray-level correction curve determined from a cumulative luminance histogram, but the characterization and genre of the content are not determined. Also, the gray-level correction pattern may be changed in a frame where a scene change is not detected, in which case a weighted mean of the gray-level correction curves of the present and previous frames is obtained, but the change of image quality may be undesirably noticeable.